Just reading the Thinkbroadband blog they make an interesting suggestion.
The simple idea of an http header flagging the user as a child. Perhaps it should flag within some age bands.
There are, of course, two ways to do this, and both would need web server and browser support, but they are not rocket science, and they are working at the right level and in the right place.
One side is for web sites to have a header indicating an age rating for the content. The browser could have an admin level account setting indicating the user's age, and so block any age inappropriate content.
The other side is the client could send a header with an age band, pre-set in the browser user settings at an admin level, and the server could refuse to serve age inappropriate content. This does mean giving some personal information on every web request.
Either way, but ends need to know something. The server needs to know it has some 18+ content, and the browser needs to know it has a 15 year old in front of it.
The client side is relatively simple for this, and I am sure windows, and apple, and firefox, and chrome could easily start to handle any standard that comes along - especially if it is a really simple standard. If there is a standard, I doubt there would be much opposition to this.
The server side is slightly more complex as it does mean "adult websites" owning up to being adult websites. Bear in mind that this covers a lot more than porn. Alcohol manufacturers ask web users if they are over 18, for example.
Well, they might. If porn sites are facing the prospect of countries doing default-on blocking, then they may be interested in, at least seeming to, co-operate.
In practice these sites are there to make money. They are not going to make money from minors. Showing porn to minors is wasting their resources and upsetting governments!
So they may well be happy to either mark their sites as 18+, or check "Child-Age-Band" headers sent by clients.
I think there are actually standards for this though already - for servers stating the type of content - so is this debate moot anyway.
The idea of a browser header saying an age band would be useful for more than just filtering though - sites selling goods could not offer to sell to minors.